Quick Counter For Young Children

This circuit is a toy to encourage young children to count. Power is turned on by switch S1, then S2 is closed. This makes nine LEDs flash slowly. S2 is then opened and the LEDs go out. Pressing pushbutton PB1 turns on a random number of LEDs - briefly - during which time they are to be counted. The number counted can be checked by pressing PB2 which turns the same LEDs on for as long as needed. Then repeat. The circuit works as follows: IC3 is a 4049 hex inverter connected as three oscillators running at different rates. It is turned on by closing switch S2a. The clock pulses from IC3 drive both halves of IC1 and one half of IC2, both being 4015 dual 4-stage shift registers. Each shift register has four outputs which go high in order: 1, 1 and 2; 1 and 2 and 3; 1 and 2 and 3 and 4. However as output 4 is connected to the reset line of its own half - the shift register resets to zero. Outputs 1, 2 & 3 of all three shift registers are connected to nine LEDs, the cathodes of which go to a common rail.

Circuit diagram:

Quick Counter Circuit Diagram For Young children

This rail is connected to ground via S2b when switch S2 is closed. When S2 is opened the three oscillators stop but a random number of LEDs is still connected to the high outputs of the 4015s. That number can be viewed briefly by pressing PB1 which pulses the 7555 timer in monostable mode, to give a short duration output which drives Q1 and connects the LED cathodes to 0V. The viewing time is adjustable by VR1. Checking a count is done by pressing PB2 which holds the same LEDs on as long as desired. The LEDs are set in a 3 x 3 grid with the connection scattered, ie, the first row is not the three LEDs from the first half of IC1. Note that, unlike the usual dice, a number such as 5 can appear in many formats, so pattern recognition is no help. Also note that this is not a nine output true dice - because the numbers do not come up with equal frequency.

Author: A. Lowe - Copyright: Silicon Chip

Read more

LED Noughts And Crosses

Here’s a twist to the age-old game of noughts and crosses. Instead of pen and paper, it uses nine 10mm tri-colour LEDs arranged in a 3 x 3 grid. One player has nine red buttons while the other player has nine green, set out in identical grids. The aim, of course, is to make three LEDs in a row glow the same colour – red or green! Pushing a red button causes the LED in the equivalent position on the grid to glow red in colour. Likewise, pushing a green button lights the equivalent green LED.

Circuit diagram:

LED Noughts And Crosses Circuit Diagram

If a player pushes a button for a LED that is already glowing red or green, then that LED changes to yellow, exposing the false move! All the LEDs are then turned off, ready for the next game, by pressing the "Clear" button. For simplicity, the circuit shows only one tri-colour LED and a pair of opposing buttons. This circuit fragment must be repeated another eight times to create a complete 3 x 3 grid. A brief press on a button fires the associated SCR and turns on the LED. The common (cathode) lead of all LEDs is connected to the 0V rail via the normally-closed contacts of the "Clear" pushbutton (S3).

Author: A. J. Lowe - Copyright: Silicon Chip Electronics

Read more

Soldering Iron Tip Preserver

Although 60/40 solder melts at about 200&degC, the tip temperature of a soldering iron should be at about 370&degC. This is necessary to make a good quick joint, without the risk of overheating delicate components because the iron has to be kept on the joint for too long. Unfortunately, at this temperature, the tip oxidises rapidly and needs constant cleaning. That's where this circuit can help - it keeps the soldering tip to just below 200&degC while the iron is at rest.

Oxidisation is then negligible and the iron can be brought back up to soldering temperature in just a few seconds when needed. In addition, normal soldering operation, where the iron is returned to rest only momentarily, is unaffected because of the thermal inertia of the iron. Two 555 timers (IC1 & IC2) form the heart of the circuit. IC1 is wired as a monostable and provides an initial warm-up time of about 45 seconds to bring the iron up to temperature. At the end of this period, its pin 3 output switches high and IC2 (which is wired in astable configuration) switches the iron on - via relay RLY1 - for about one second in six to maintain the standby temperature.

Circuit diagram:

Soldering Iron Tip Preserver Circuit Diagram

The presence of the iron in its stand is sensed by electrical contact between the two and some slight modification of the stand may be necessary to achieve this. When the iron is at rest, Q1's base is pulled low and so Q1 is off. Conversely, when the iron is out of its stand, Q1 turns on and pulls pins 2 & 6 of IC2 high, to inhibit its operation. During this time, pin 3 of IC2 is low and so the iron is continuously powered via RLY1's normally closed (NC) contacts. Note that the particular soldering iron that the circuit was designed for has its own 24V supply transformer. Other irons may need different power supply arrangements. The warm-up time and standby temperature can be varied by altering R2 and R5, as necessary.
Author: Alan March - Copyright: Silicon Chip Electronics

Read more

Gym Agility: A Simple Strategy Game

This simple circuit is a two-person game of strategy and speed - and potentially, agility and athletic fitness. Each player has a row of four LEDs before him/her. Beside each LED, there is a pushbutton which, when pressed, lights up the corresponding LED. The aim of the game is for a player to illuminate all four of their LEDs in a row, in which case the circuit declares a winner. However, there is a catch. As soon as you light one of your own LEDs, the other player's corresponding LED goes out - and vice versa.

The game begins by giving each player two illuminated LEDs. Consider now that this game is scaled up and used in a gym. If the LEDs in the circuit are directly replaced with N-channel power MOSFETs, then 12V globes can be illuminated (a MOSFET's gate is wired in place of a LED's anode, the source goes to negative, and the load is wired between the drain and positive). If four large pushbuttons are mounted on one wall and four on another, this could become a game of agility - if not a physical tussle to keep the other player away from critical push-buttons.

Circuit diagram:

Gym Agility Circuit Diagram

Here's how the circuit works:

Schmitt NAND gate IC1a and IC1b (4093) form a simple bistable latch. When one output (pin 3) goes "high", the other output (pin 4) goes "low" and vice versa. The main advantage of using a bistable latch (as opposed to a flipflop) is that it does not suffer from switch bounce. Four such bistable latches are fed to inputs A-D of IC2. However, for the sake of simplicity, only one of these is shown; ie, IC1a-IC1b. We now need to identify when all four bistable latches go either "high" or "low".

This is done using IC2, a 4067 16-channel multiplexer. When inputs A-D are all "low" (binary 0000), this opens decimal channel 0. Conversely, when all are "high" (binary 1111), this opens decimal channel 15. Channels 0 and 15 thus trigger a win for one side or the other, by taking pins 9 or 16 of IC2 "low". Finally, if the game is quite hectic, a win might only last for a fraction of a second before it is lost again. Therefore, IC1c and IC1d are wired as timers, which do not permit any further play until a win has been reported for one or two seconds - either via LED3 or LED4. During this time, however, the players' buttons may be pressed to reset the game to two LEDs all.

Author: Thomas Scarborough - Copyright: Silicon Chip Electronics Magazine

Read more

Heart Rate Monitor

Strictly speaking, this simple circuit shouldn't work! How could anyone expect an ordinary light dependent resistor photo cell to 'see' through a fingertip in natural daylight and detect the change in blood flow as the heart pulsates? The secret is a high gain circuit, based on a dual op amp IC which can be either the low power LM358 or the JFET TL072. The LDR is connected in series across the 9V battery supply via a 100kO resistor (R1) and the minute signal caused by the blood pulsing under the skin is fed to the non-inverting (+) input, pin 3, of IC1a via a 0.µF capacitor.

Pin 3 is biased by a high impedance voltage divider consisting of two 3.3MO resistors. The feedback resistors to pin 2 set the gain to 11 times. The output of IC1a is fed via a 0.47µF capacitor and 220kO resistor to IC1b. This is configured as an inverting op amp with a gain of 45 so that the total circuit gain is about 500. The output of IC1b is used to drive an analog meter which may be a multimeter set to the 10V DC range or any panel meter in series with a resistor to limit the current to less than its full-scale deflection. The prototype used an old VU meter with a 47kO resistor fitted in series.

Circuit diagram:

Heart Rate Monitor Circuit Diagram

Note that the unit was designed to use the Dick Smith Electronics light dependent resistor (Z-4801). Other LDRs may require a change in the value of resistor R1. A light source such as a high brightness LED is not required. All that is needed is a reasonably well-lit room, preferably natural daylight, to produce a healthy swing of the needle. Only when the hands are very cold does it make it a little more difficult to accurately count the pulses. To check your heart rate, carefully position your thumb or finger over the LDR and count the meter fluctuations for a period of 15 seconds. Then multiply the result by four to obtain your pulse rate. The circuit can not be used if you are walking or running, etc.
Author: Tony Lee
Copyright: Silicon Chip Electronics Magazine

Read more

Call Acknowledged

This circuit could be used (depending on your circumstances) by a gentleman to summon his butler, a manager his secretary or as in the author’s case to call the kids down to dinner without having to shout above the level of the CD player/TV/games console in their bedroom. Rather than resorting to a full-blown intercom system, a simpler solution was envisaged and while a buzzer could easily fulfil this function, this circuit has the advantage of providing a visual indication of a call as well as confirming to the caller that the ‘message’ has been received.

This is especially useful in the latter case, as the call may be easily drowned out by the music playing in the headphones. The circuit, which requires no complicated switching, uses a simple two-wire connection between the two stations and utilises the fact that the forward voltage drop of a blue (or white) LED is greater than that of a red, green or yellow one. The circuit is based on a two-transistor multivibrator which is used to pulse a red LED (D3) as well as the buzzer Bz1 on and off at about 1.5 Hz when push button S1 is closed. This frequency may of course be altered if required by changing the values of the capacitors.

Circuit diagram:

Call Acknowledged Circuit Diagram

The diode D1 in series with the collector of transistor T2 is required to isolate the output from the effects of the buzzer circuitry, which would alter the multivibrator frequency. In principle, the multivibrator could be dispensed with but a pulsed buzzer/flashing led is much more noticeable than a continuous signal especially in noisy conditions. Since the voltage across a red LED is typically about 1.5 V while a blue LED requires at least 2.5 V to 3 V to light, the blue LED will remain off when the call button S1 is pressed. Despite being rated for operation at 3-12 V, most piezo sounders can still produce a piercing sound from the pulsed 1.5-V available across the red LED which should get the attention of even the most preoccupied teenager.

When the recipient presses the acknowledge (push to break) switch S2, the red LED/buzzer are disconnected allowing the blue LED to flash at the sending station indicating to the caller that his call has been received. Alternatively, if a blue LED is not available, a red or green type in series with a forward biased silicon diode to raise its forward voltage above that of the red LED in the receiver could be used instead. The circuit may be powered by a 9-V battery, a mains power supply being unnecessary in view of the low power consumption and infrequency of use of the circuit.

Author: Bart Trepak - Copyright: Elektor Electronics

Read more

Transcutaneous Electrical Nerve Stimulator (TENS)

A Transcutaneous Electrical Nerve Stimulation (TENS) device is, put bluntly, a machine for giving electric shocks. The author was prescribed such a device on loan by his orthopaedic specialist. The unit has a large number of programmes, of which he used only one. Measuring the signals at the output of the device in this mode revealed damped oscillations at a frequency of approximately 2.5 kHz, with a repetition rate of approximately 100 Hz.

Circuit diagram:

Transcutaneous Electrical Nerve Stimulator Circuit Diagram

How hard can it be to make such a device ourselves? The simple circuit uses a CMOS 555 timer to produce a brief pulse which feeds a 1:10 miniature transformer. Together with a 4.7 nF capacitor the transformer makes a parallel resonant circuit: the resonance leads to a considerable increase in the output voltage. The pulse width can be adjusted using a potentiometer, here shown combined with the on-off switch. Wider pulses produce higher output voltages. Since a peak voltage of up to 200 V can be produced, the transformer must have adequate insulation: Conrad Electronics type 516260-62 is suitable. A low-cost phono socket at the output gives reliable connection to the electrode cable.

The adhesive electrodes shown in the photograph (disposable and permanent types are available) can be obtained from pharmacies and medical suppliers. They generally have connectors compatible with 2 mm banana plugs, and so it is possible to make up the necessary cable yourself. To treat responsive parts of the body, such as the arm, the potentiometer need not be turned up far to obtain the necessary sensation. Less sensitive parts, such as the knee or foot, need a rather higher voltage and hence a correspondingly higher potentiometer setting.

Author: Klaus Rohwer - Copyright: Elektor Electronics Magazine

Read more

Tablet Reminder Uses Watch Module

This device is used as a reminder to take medicine every day. This device actually contains a crystal watch and a 4001 quad 2-input NOR gate with two of the gates (IC1a & IC1b) wired as an RS flipflop. The watch is set to "tablet time", usually mornings, when an alarm is activated with a high signal fed via diode D1 which sets the RS flipflop and enables the oscillator comprising gates IC1c & IC1d. This drives the LED with a 10% duty cycle. The 10nF capacitor resets the watch alarm when positive voltage appears on pin 3 of IC1. The circuit consumes only 50µA with a 3V battery.

Circuit diagram:

Tablet Reminder Circuit Diagram

Author: Rasim Kucalovic

Read more

123 Game - All MCU-free

This electronic game pits a human player against the ‘machine’. The opponents use a common ‘game token’ and take turns moving along a path by one, two or three steps, and the winner is the first one to reach the goal exactly. Incredibly enough, this simple version of the ‘123’ game can be built without a microcontroller, and it’s almost impossible to beat. The electronics for this is built using only diode logic (Figure 1).

The ‘ input inter face’ consists essentially of 30 miniature sockets to which a probe tip can be connected to mark the position of the ‘game token’. To make the game more compact, the sockets are arranged in a grid so the route along the sockets follows a serpentine path (Figure 2). The starting position is at the bottom right, and the goal is in the middle of the playing area. The electronics becomes the ‘active player’ when the button is pressed.

The number of steps it wants to move is shown by three LEDs (one, two or three LEDs light up) at the top of the playing area. Naturally, the human player must move the ‘game token’ for the machine opponent. The winner is the first one to reach the goal exactly. How can such simple circuitry represent such a formidable opponent? As already mentioned, the path from the start to the goal is formed by 30 sockets. Each socket has an associated ideal next move.

There are three possibilities, of course: 1, 2 or 3. As you can see from the schematic diagram, switch S1 closes the circuit (which means the player asks the ‘computer’ how many steps it wishes to move) if the probe is touching one of the sockets. All 30 sockets are classified into three types, represented in the schematic diagram by one socket for each type. All sockets belonging to a particular type are simply connected together electrically, which is not shown on the schematic diagram for the sake of clarity.

Circuit diagram:

123 Game Circuit Diagram- Microcontroller-Free

This is how the LED display works:

The player touches the right-hand contact with R4 (only LED D3 lights up), the left-hand contact with R3 (LEDs D1 and D2 light up), or the middle contact with diodes D4 and D5 (all three LEDs light up). The two diodes prevent all three LEDs from lighting up if the player touches the left-hand or right-hand contact. The key to all this lies in the assignment of the 30 sockets to the three types of logic, which means the three types of ideal next move.

Working backward from the goal, no further move is possible when the goal is reached. For this reason, the last socket is not connected to anything. At the socket just before the goal, the ‘computer’ naturally wants to be exactly one step in front. Consequently, this socket is connected to R4. At the second socket before the goal, the electronics wants to move by two steps. This socket is thus connected to R3.

Obviously, three moves before the finish, a three-step is best as it leads to instant victory. Consequently this socket is connected to D4/D5. The correct response of the ‘computer’ is shown in Figure 2 by the number next to each position. As the two opponents take turns playing, the electronics always tries to arrive at a strategically favourable position (marked by the arrows). If the electronics manages to reach one of these positions, it’s impossible for the human player to win. This means that the human player can only win by starting first and always making the right move.

Stefan Hoffmann
Elektor Electronics 2008

Read more

Pulse Generator And Signal Tracer Circuit Diagram

Dual-purpose test-instrument, Very simple circuitry, 1.5V Battery-operated

This simple circuit generates narrow pulses at about 700-800Hz frequency. The pulses, containing harmonics up to the MHz region, can be injected into audio or radio-frequency stages of amplifiers, receivers and the like for testing purposes. A high-pitched tone can be heard from the speaker of the device under test when all is working properly. The clip must be connected to the ground of the device under test, touching with the probe the different stages of the circuit, starting from the last stage and going up towards the first. When the tone is no longer heard, the defective stage has been found.

Connecting an earclip or headphone to J1, the circuit will automatically change into a two-stage amplifier and any audio signal coming from the device under test and picked-up by the probe will be heard through the headphones. The testing of a circuit should be made in the reverse manner, i.e. starting from the first stage and going down until the last stage. When nothing is heard, the defective stage has been found.

Circuit diagram:

Parts:

R1__________________1M 1/4W Resistor
R2,R4_______________2K7 1/4W Resistors
R3________________150K 1/4W Resistor
C1__________________2n2 630V Ceramic or Polyester Capacitor (See Notes)
C2,C3_______________4n7 63V Ceramic or Polyester Capacitors
D1_______________1N4148 75V 150mA Diode
Q1________________BC547 45V 100mA NPN Transistor
Q2________________BC557 45V 100mA PNP Transistor
SW1________________SPST miniature Slider Switch (See Notes)
J1_________________Stereo switched 3mm. Jack socket (See Notes)
Probe______________Metal Probe 3 to 5 cm. long
Clip_______________Miniature Crocodile Clip
B1_________________1.5V Battery (AA or AAA cell etc.)

Circuit operation:

Q1 & Q2 form a complementary astable multivibrator, whose operating frequency is set mainly by R3, C2 & C3 values. Output pulses are taken at Q2 Collector and applied to the probe by means of decoupling capacitor C1. D1 provides a symmetrical shape for the output waveform.
If an earclip or headphone jack is plugged into J1, the connection from Q2 Collector and C1 - C2 is broken by the switch incorporated into J1: in this case the circuit becomes a two-stage amplifier.

Notes:

• If you intend to use the circuit to test valve operated devices C1 must be a 630V type. Working with low voltage supply transistor devices the voltage of C1 can be lowered to 63 or 100V.
• If instead of a short probe, you intend to connect the circuit to the device under test by means of a piece of wire longer than a few centimeters, a small ceramic capacitor (470 to 1000pF) should be added in parallel to D1 to prevent unwanted RF oscillation.
• Current drawing when in Pulse-Generator mode is about 60µA and 1.2mA when in Signal-Tracer mode operation. Therefore SW1 can be omitted, provided that the earclip or headphones are unplugged when the circuit is unused.
• J1 is a stereo switched jack socket wired to obtain a series connection of the two earpieces forming a stereo headphone. In this manner the circuit is loaded with a higher impedance and sensitivity will be improved.
• Therefore, the higher the load impedance the more sensitive the Signal-Tracer. In any case, common 32 Ohm impedance mini-headphones suitable for walkman sets will work fine.
• A crystal (high impedance) earpiece is a good solution, provided you substitute J1 with a mono switched jack socket.
• The entire circuit can be easily fitted into a pen-like enclosure, with the probe protruding like a nib.

Source: www.RedCircuits.com

Read more

Whistle Responder Schematic - Circuit Diagram

Beeps when hears your whistle, A gadget suitable for key-holders, games etc.

Some 20 years ago it was common to see small key-holders emitting an intermittent beep for a couple of seconds after its owner whistled. These devices contained a special purpose IC and therefore were not suited to home construction. The present circuit is designed around a general purpose hex-inverter CMos IC and, using miniature components and button clock-type batteries can be enclosed in a matchbox. It is primarily a gadget, but everyone will be able to find suitable applications.
Circuit operation:
This device beeps intermittently for about two seconds when a person in a range of around 10 meters emits a whistle. The first two inverters contained in IC1 are used as audio amplifiers. IC1A amplifies consistently the signal picked-up by the small electret-microphone and IC1B acts as a band-pass filter, its frequency being centered at about 1.8KHz. The filter is required in order to select a specific frequency, the whistle's one, stopping other frequencies that would cause undesired beeper operation. IC1C is wired as a Schmitt trigger, squaring the incoming audio signal. IC1D is a 2 second-delay monostable driving the astable formed by IC1E & IC1F. This oscillator generates a 3 to 5Hz square wave feeding Q1 and BZ1, thus providing intermittent beeper operation.

Circuit diagram:

Whistle Responder Circuit Diagram

Parts:

R1 = 22K 1/4W Resistor
R2 = 10K 1/4W Resistor
R3 = 4M7 1/4W Resistor
R4 = 100K 1/4W Resistors
R5 = 220R 1/4W Resistor
R6 = 330K 1/4W Resistor
R7 = 47K 1/4W Resistor
R8 = 100K 1/4W Resistors
R9 = 2M2 1/4W Resistor
R10 = 1M5 1/4W Resistor

C1 = 47nF 63V Polyester or Ceramic Capacitors
C2 = 10nF 63V Polyester Capacitors
C3 = 10nF 63V Polyester Capacitors
C4 = 1µF 63V Electrolytic Capacitors
C6 = 1µF 63V Electrolytic Capacitors
C5 = 47nF 63V Polyester or Ceramic Capacitors

D1 = 1N4148 75V 150mA Diodes
D2 = 1N4148 75V 150mA Diodes
Q1 = BC337 45V 800mA NPN Transistor
B1 = 2.8 or 3V Battery (see notes)
IC1 = 4049 Hex Inverter IC
BZ1 = Piezo sounder (incorporating 3KHz oscillator)
MIC1 = Miniature electret microphone

Notes:

• Power supply range: 2.6 to 3.6 Volts.
• Standing current: 150µA.
• Depending on dimensions of your box, you can choose from a wide variety of battery types:
• 2 x 1.5 V batteries type: AA, AAA, AAAA, button clock-type, photo-camera type & others.
• 2 x 1.4 V mercury batteries, button clock-type.
• 1 x 3 V or 1 x 3.6 V Lithium cells.

Read more

Cranial Electrotherapy Stimulator Circuit Diagram

Current generated flows through clips placed on the earlobes
Output current adjustable from 80 to 600 microAmperes

Owing to the recent launching in Europe of Cranial Electrotherapy Stimulation (CES) portable sets, we have been "Electronically Stimulated" in designing a similar circuit for the sake of hobbyists. CES is the most popular technique for electrically boosting brain power, and has long been prescribed by doctors, mainly in the USA, for therapeutic reasons, including the treatment of anxiety, depression, insomnia, and chemical dependency. CES units generate an adjustable current (80 to 600 microAmperes) that flows through clips placed on the earlobes.

The waveform of this device is a 400 milliseconds positive pulse followed by a negative one of the same duration, then a pause of 1.2 seconds. The main frequency is 0.5 Hz, i.e. a double pulse every 2 seconds. Some people report that this kind of minute specialized electrical impulses contributes to achieve a relaxed state that leaves the mind alert. Obviously we can't claim or prove any therapeutic effectiveness for this device, but if you are interested in trying it, the circuit is so cheap and so simple to build that an attempt can be made with quite no harm.

Circuit diagram:

Parts:

R1_____________1M5 1/4W Resistor
R2____________15K 1/4W Resistor
R3___________100K Linear Potentiometer
R4_____________2K2 1/4W Resistor
C1___________330nF 63V Polyester Capacitor
C2___________100µF 25V Electrolytic Capacitor
D1_____________3mm. Red LED
IC1___________7555 or TS555CN CMos Timer IC
IC2___________4017 Decade counter with 10 decoded outputs IC
SW1___________SPST Slider Switch
B1______________9V PP3 Battery Clip for PP3 Battery
Two Earclips with wires (see notes)

Circuit operation:

IC1 forms a narrow pulse, 2.5Hz oscillator feeding IC2. This chip generates the various timings for the output pulses. Output is taken at pins 2 & 3 to easily obtain negative going pulses also. Current output is limited to 600µA by R2 and can be regulated from 80 to 600µA by means of R3. The LED flashes every 2 seconds signaling proper operation and can also be used for setting purposes. It can be omitted together with R4, greatly increasing battery life.

Notes:

• In order to obtain a more precise frequency setting take R1=1M2 and add a 500K trimmer in series with it.
• In this case use a frequency meter to read 2.5Hz at pin 3 of IC1, or an oscilloscope to read 400msec pulses at pins 2, 3 or 10, adjusting the added trimmer.
• A simpler setting can be made adjusting the trimmer to count exactly a LED flash every 2 seconds.
• Earclips can be made with little plastic clips and cementing the end of the wire in a position suited to make good contact with earlobes.
• Ultra-simple earclips can be made using a thin copper foil with rounded corners 4 cm. long and 1.5 cm. wide, soldering the wire end in the center, and then folding the foil in two parts holding the earlobes.
• To ensure a better current transfer, this kind of devices usually has felt pads moistened with a conducting solution interposed between clips and skin.
• Commercial sets have frequently a built-in timer. Timing sessions last usually 20 minutes to 1 hour. For this purpose you can use the Timed Beeper the Bedside Lamp Timer or the Jogging Timer circuits available on this website, adjusting the timing components in order to suit your needs.

Source: www.RedCircuits.com

Read more

Pills Reminder

4 - 6 - 8 - 12 - 24 - 48 hours setting, LED or Beep Alert - 9V Battery Supply

A Pills Reminder is a device that operates a flashing LED (and/or a beeper) at a fixed hour interval. A choice of time-intervals as wide as possible is available with this circuit, namely 4, 6, 8, 12, 24 and 48 hours. At first you must choose the hour interval by switching SW1 to the desired value, then apply power by means of SW2. After the hour delay chosen has elapsed the LED will start flashing at 2Hz, i.e. two times per second. This status will last until pushbutton P1 is pressed: then the LED will turn off, but the circuit will continue its counting and the LED will flash again when the same hour interval as before is reached. A noteworthy feature of this circuit, usually not found in similar devices, is that the internal counter is not reset when P1 is pressed: this allows a better time-interval precision.

Let us explain this feature with an example: suppose you have set the time interval to 24 hours and started the Pills Reminder at 8 o'clock. Next day, at 8 o'clock the LED will start flashing, but you, for some reason, notice the flashes at 8:10 and press P1 to stop the LED. With most devices of this kind, the counter will be reset, causing the LED to start flashing next day at 8:10 o'clock. This will not happen with this circuit and the LED will start flashing next day always precisely at 8 o'clock even if you pressed P1 at 9 or 10 o'clock.

Circuit diagram:

Pills Reminder Circuit Diagram

Parts:

R1______________10M 1/4W Resistor
R2,R3,R4_______100K 1/4W Resistors
R5,R7___________10K 1/4W Resistors
R6_______________1K 1/4W Resistor
C1,C2___________22pF 63V Ceramic Capacitors (See Notes)
C3______________22µF 25V Electrolytic Capacitor
C4,C5__________100nF 63V Polyester Capacitors
C6_______________1µF 63V Polyester, Multilayer Ceramic or Electrolytic Capacitor
IC1____________4060 14 stage ripple counter and oscillator CMos IC
IC2____________4040 12 stage ripple counter CMos IC
IC3____________4082 Dual 4 input AND gate CMos IC
IC4____________4075 Triple 3 input OR gate CMos IC
IC5____________4520 Dual binary up-counter CMos IC
IC6____________4001 Quad 2 input NOR Gate CMos IC
D1_____________5 or 10mm red LED
XTAL_________32.768 kHz Sub-miniature Watch crystal
P1_____________SPST Pushbutton
SW1____________2 poles 6 ways Rotary Switch
SW2____________SPST Toggle or Slide Switch
B1_______________9V PP3 Battery Clip for PP3 Battery

Alternative Clock Parts:

R8_______________1K 1/4W Resistor
R9_____________330K 1/4W Resistor
R10_____________20K 1/2W Cermet or Carbon Trimmer
R11______________1K 1/2W Cermet or Carbon Trimmer
C7_______________1µF 63V Polyester Capacitor
IC7____________7555 or TS555CN CMos Timer IC

Circuit Operation:

The clock of the circuit is made of a stable oscillator built around two inverters embedded into IC1 and a Watch crystal oscillating at 32.768kHz. This frequency is divided by 16384 by the internal flip-flop chain of IC1 and a 2Hz very stable clock frequency is available at pin #3 of this IC. IC2 counter and IC3A 4 input AND gate are wired in order to divide by 3600 the 2Hz clock, therefore, a pulse every 30 minutes is available at the clock input of IC5. The division factor of this IC is controlled by IC3B and the position of SW1A and B, selecting from six time-intervals fixed to 4, 6, 8, 12, 24 and 48 hours.

The set-reset flip-flop formed by IC6B and IC6C is set through IC4C each time a low to high transition is present at the pin of IC5 selected by SW1B cursor. IC6A and C4 provide to set the flip-flop also when a high to low transition is present at SW1B cursor. When the flip-flop is set, IC6D is enabled and the 2Hz frequency available at pin #3 of IC1 is applied to pin #13 of IC6D causing the flashing LED operation. The flip-flop can then be reset by means of P1. A master reset is automatically done at switch on by means of C6 and R7.

Alternative Clock:

Sometimes, the Watch crystal can be difficult to locate, or could be considered too expensive. For those willing to avoid the use of a Watch crystal and to accept less time accuracy, an alternative clock generator circuit is provided, directly oscillating at 2Hz, thus avoiding the use of divider ICs. A CMos 7555 Timer IC generates a stable 2Hz square wave, whose frequency must be accurately set by means of two trimmers. R10 must be adjusted first for coarse tuning, then R11 for fine tuning. Setting precisely the 2Hz frequency of this oscillator is a rather difficult task, and can be done with great patience and the aid of a clock, a chronometer or, best, a digital frequency meter capable of measuring very low frequencies. In any case, after an accurate setup, this oscillator showed a very stable performance, not affected by battery voltage variations and an accuracy of about ±30 seconds per 24 hours interval.

Notes:

• Wanting the utmost time precision and if a digital frequency meter is available, a 5-50pF 50V Ceramic Trimmer Capacitor can be used in place of C2. It must be adjusted in order to read exactly 32.768kHz on the meter display with the input probe connected to pin #9 of IC1.
• A Piezo sounder (incorporating a 3KHz oscillator) can be added to provide a visual plus audible alert. It must be wired across pin #11 of IC6D and negative ground, respecting polarities. Remove D1 and R6 if the visual alert is not needed.

Author: RedCircuits - Copyright: www.redcircuits.com

Read more

LED Chaser Provides Three Game Functions

This circuit is essentially a light chaser but it can also be set to provides heads or tails (Two Up) or a Dice (die). It also has a speaker to simulate the sound of a spinning roulette wheel. Note that the dice and heads/tails features can be deleted if required and rules for the games created to suit individuals; eg, betting can be used or the numbers recorded and then totalled to get the highest score per game. IC1 is a 4046 phase locked loop (PLL) but only the voltage controlled oscillator (VCO) portion of the chip is used to provide the clock pulse for IC2, a 4017 decade counter/divider. In roulette wheel mode, switch S3 is pushed to start the game.

Circuit diagram:

This charges the 10μF capacitor at pin 9 and as the capacitor discharges, the output frequency is slowly reduced to slow the rate of the chaser LEDs driven by IC2. In chaser mode, switch S2 is closed to provide a fixed frequency output from IC1. This can be varied over a wide range with potentiometer VR1. Transistor Q1 is also driven by the oscillator output of IC1 and it drives the speaker. Trimpot VR2 varies the sound level while switch S4 turns it off. Switch S5 selects Die or other (chaser/roulette). In Die mode, pin 6 is connected to the reset, pin 15, so that the circuit only counts to 6 whereas in the other modes it counts to 10 and displays all LEDs. Pin 12 drives transistor Q2 and two LEDs to provide the Heads/Tails function.

Author: John McCuaig - Copyright: Silicon Chip Electronics

Read more

Sleeping Aid Schematic - Circuit Diagram

Based on electromagnetic-field radiation, Place it under the pillow - Built-in timer

Many people experienced sleeping well in natural surroundings, into a tent or a wooden hut. This fact is due not only to the healthy atmosphere but also from our unconscious ability to perceive natural Earth's magnetic-fields. The circuit generates this type of Geo-magnetic-fields and lets us perceive them: in this manner our brain is surrounded by an ideal environment for a sound sleep. (N.B. Basic ideas for this circuit are coming from German papers).
Circuit operation:
IC2C and IC2D generate two square waves at about 1.2 and 5 Hz respectively. These wave-forms are converted into 60µS pulses at the same frequencies by means of C5 & C6 and mixed at Q1 Base. This transistor drives the Radiator coil with a scalar series of pulses of 60µS length and 9V amplitude. IC1, IC2A & IC2B form the timer section.

C1 & R2 provide auto-reset of IC1 at switch-on. The internal oscillator of IC1 drives the 14 stage ripple counter and, after about 15 minutes, output pin 1 goes high. Pin 3 of IC2A goes low and stops IC2C & IC2D oscillation. If SW2 is left open (Alternate mode operation), after 15 minutes pin 1 of IC1 goes low, pin 3 of IC2A goes high and oscillators are enabled again.

If SW2 is closed (Stop mode operation), the first time output pin 1 of IC1 goes high, the internal oscillator of the IC is disabled by means of D1. Therefore the circuit remains off until a reset pulse is applied to pin 12 by means of P1 or when the whole device is switched-off and then restarted. The same thing occurs when SW1 is switched on 30 or 60 minutes positions, obviously changing time length.

IC2B drives pilot LED D2 which operates in the following three modes:

• flashes quickly and almost randomly when the Radiator coil is driven
• flashes somewhat slowly and regularly when the Radiator coil is pausing during the Alternate mode operation
• is off when the circuit auto-stops (Stop mode operation)

Circuit diagram:

Sleeping Aid Circuit Diagram

Parts:

R1 = 1K 1/4W Resistors
R2 = 10K 1/4W Resistor
R3 = 10M 1/4W Resistors
R4 = 2M2 1/4W Resistors
R5 = 1K 1/4W Resistors
R6 = 10M 1/4W Resistors
R7 = 2M2 1/4W Resistors
R8 = 4K7 1/4W Resistors
R9 = 4K7 1/4W Resistors

C1 = 47µF 25V Electrolytic Capacitors
C2 = 100nF 63V Polyester Capacitor
C3 = 330nF 63V Polyester Capacitors
C4 = 330nF 63V Polyester Capacitors
C5 = 15nF 63V Polyester Capacitors
C6 = 15nF 63V Polyester Capacitors
C7 = 47µF 25V Electrolytic Capacitors

D1 = 1N4148 75V 150mA Diodes
D2 = LED (any type) (see Notes)
D3 = 1N4148 75V 150mA Diodes
D4 = 1N4148 75V 150mA Diodes
D5 = 1N4148 75V 150mA Diodes

IC1 = 4060 14 stage ripple counter and oscillator IC
IC2 = 4093 Quad 2 input Schmitt NAND Gate IC
Q1 = BC327 45V 800mA PNP Transistor
L1 = Radiator coil (see Notes)
P1 = SPST Pushbutton
SW1 = 2 poles 4 ways rotary switch
SW2 = SPST Slider Switch
B1 = 9V PP3 Battery, Clip for PP3 Battery

Features:

• Generates a natural electromagnetic-field
• Makes easier to fall asleep
• Induces a prolonged and sound sleep without drugs
• No side effects

Use of this circuit:

• Select a timing option by means of the rotary switch SW1.
• Choose 15, 30 or 60 minutes operation.
• Select "Stop" or "Alternate" mode operation by means of SW2.
• With SW2 closed (Stop mode operation) the electromagnetic radiation stops after the pre-set time is elapsed.
• With SW2 opened (Alternate mode operation) the device operates for the pre-set time, then pauses for the same amount of time: this cycle repeats indefinitely.
• Place the unit under the pillow and sleep like a log.
• To reset a cycle press P1 pushbutton.

Notes:

• L1 is obtained by winding randomly 600 turns of 0.2 mm. enameled wire on a 6 mm. diameter, 40 mm. long, steel bolt. Secure the winding with insulating tape.
• Mean current drawing is about 7mA, decreasing to less than 4mA during pauses when in Alternate mode operation.
• Battery life can be dramatically increased omitting LED D2 and its associated resistor R5.
• Use a plastic box to enclose the circuit: metal cases can severely limit electromagnetic radiation.

Source: extremecircuits.net

Read more

Digital Step-Km Counter Circuit Schematic

Max. Range: 9,950 meters with two digits slip it in pants' pocket For walking and jogging

This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot illuminates after every 50 meters of walking.
A beeper (excludable), signals each count unit, occurring every two steps. A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on.

For low battery consumption the display illuminates only on request, pushing on P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together. Obviously, this is not a precision meter, but its approximation degree was found good for this kind of device. In any case, the most critical thing to do is the correct placement of the mercury switch inside of the box and the setting of its sloping degree.

Circuit diagram:

Digital Step-Km Counter Circuit Diagram

Parts:

R1 = 22K 1/4W Resistor
R2 = 2.2M 1/4W Resistor
R3 = 22K 1/4W Resistor
R4 = 1M 1/4W Resistor
R5 = 4.7K 1/4W Resistor
R6 = 47R 1/4W Resistor
R7 = 4.7K 1/4W Resistor
R8 = 4.7K 1/4W Resistor
R9 = 1K 1/4W Resistor

C1 = 47nF 63V Polyester Capacitor
C2 = 100nF 63V Polyester Capacitor
C3 = 10nF 63V Polyester Capacitor
C4 = 10µF 25V Electrolytic Capacitor

D1 = Common-cathode 7-segment LED mini-display (Hundreds meters)
D2 = Common-cathode 7-segment LED mini-display (Kilometers)

Q1 = BC327 45V 800mA PNP Transistors
Q2 = BC327 45V 800mA PNP Transistors

P1 = SPST Pushbutton (Reset)
P2 = SPST Pushbutton (Display)

IC1 = 4093 Quad 2 input Schmitt NAND Gate IC
IC2 = 4024 7 stage ripple counter IC
IC3 = 4026 Decade counter with decoded 7-segment display outputs IC
IC4 = 4026 Decade counter with decoded 7-segment display outputs IC

SW1 = SPST Mercury Switch, called also Tilt Switch
SW2 = SPST Slider Switch (Sound on-off)
SW3 = SPST Slider Switch (Power on-off)

BZ = Piezo sounder
B1 = 3V Battery (2 AA 1.5V Cells in series)

Circuit operation:
IC 1A & IC 1B form a monostable multi vibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divides by 64. Q2 drives the LED dot-segment of D1 every 32 pulses counted by IC2. Either IC3 & IC4 divide by 10 and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each monostable count. Q1 drives the piezo sounder and SW2 allows disabling the beep.

Notes:

• Experiment with placement and sloping degree of mercury switch inside the box: this is very critical.
• Try to obtain a pulse every two walking steps. Listening to the beeper is extremely useful during setup.
• Trim R6 value to change beeper sound power.
• Push P1 and P2 to reset.
• This circuit is primarily intended for walking purposes. For jogging, further great care must be used with mercury switch placement to avoid undesired counts.
• When the display is disabled current consumption is negligible, therefore SW3 can be omitted.

Source: extremecircuits.net

Read more

Low-Cost Dual Digital Dice

This simple dual digital dice is based on three low-cost ICs, a few transistors and a handful of LEDs. IC1a & IC1b operate as an oscillator with a frequency of about 4kHz and this clocks IC2. The frequency of oscillation is not critical - it simply needs to be high enough to prevent cheating. IC2 and IC3 are 4516 binary counters, configured to count in binary from 1-6. A power-on reset is not required here since, if the initial state is outside the correct range, the counters will count into the correct range after a few clock pulses. Let's first consider how IC2 operates. When the counter reaches "7" (ie, 111), the AND gate formed by diodes D1 & D2 and the 47kO resistor applies a high to the PE pin (pin 1).

Circuit diagram:

Low-Cost Dual Digital Dice Circuit Diagram

This presets the counter to 1 (ie, 001) and so PE goes low again. The counter then increments in the normal manner until it reaches "7" again. Counter IC3 operates in the same manner except that the clock signal is derived from IC2's O3 output. The counter outputs (O1, O2 & O3) drive NPN transistors Q1-Q6 and these in turn drive the LEDs (ie, the LEDs indicate the states of the counters). Normally, the counters are incrementing continuously and the LEDs all appear to be lit. However, when push-button switch S1 is pressed, pin 6 of IC1c goes low and pin 9 of IC1d pulls the Ci input of IC2 high, thus stopping the counters. Finally, toggle switch S2 allows the user to choose between having two dice operating simultaneously or just one.

Author: Len Cox - Copyright: Silicon Chip Electronics

Read more

Model Railway Turnout Control

This small circuit can be used to control model railway turnouts operated by AC voltages. A logic level in the range of 5–12 V can be used as the control signal. The coils of the turnout are switched using triacs. Changes in the logic level of the input signal are passed on by the buffer stage built around T1 and T2. The buffer stage is included to boost the current available at the gates of the triacs. If the input goes high, this positive change is passed through via C1. That causes a positive current to flow through D2 (D2 is reverse biased) to the gate of T3. That triac switches on, and power is applied to the turnout coil.

Circuit diagram:

Model Railway Turnout Control Circuit Diagram

This situation persists until C1 is fully charged. No more current flows after that, so the triac does not receive any gate current and switches off. If the input is set low, a negative current flows briefly via C1. It can flow through D2, but not through D1. T4 is switched on now, and the other turnout coil is energised. This circuit takes advantage of the fact that triacs can be triggered by negative as well as positive gate currents. If the turnout coils are energised for too long, you should reduce the value of C1.

If they are not energised long enough, increase the value of C1. The TIC206D can handle several ampères, so it can easily drive just about any type of turnout coil. You can also use a different type of triac if you wish. However, bear in mind that the TIC206 requires only 5 mA of gate current, while most triacs want 50 mA. That will cause the switching times to become quite short, so it may be necessary to reduce the value of R1.
Author: Hans Zijp - Copyright: Elektor Electronics

Read more

Dicing With LED's

Every self-respecting DIYer makes his own electronic dice with LEDs as spots. Then you don’t have to throw the dice anymore – just push the button. The electronics also ensures that nobody can try to improve his luck by fiddling with the dice. Too bad for sore losers! This circuit proves that an electronic die built using standard components can be made quite compact. The key component of here is a type 4060 digital counter (IC1).

This IC has an integrated oscillator stage, so only two resistors (R7 and R8) and a capacitor (C7) are necessary to generate the clock signal. The clock signal is divided by various factors by the internal digital circuitry of the IC. The division factors are designated by ‘CT’ in the IC drawing symbol. For instance, the signal on the CT3 output (pin 7) is a square wave with a frequency equal to the clock frequency divided by 23 (8). The clock signal is divided by 24 (16) on the CT4 output, by 25 (32) on the CT5 output, and so on. This means the output signals form a binary number that Dicing with LEDs counts upwards, which is naturally what a counter does.

Circuit diagram:

Of course, a die has only six possible values marked on the six sides of a cube. This means that at least three bits (the first three outputs) of the counter are necessary to drive a display. Eight different counter states (23) can be represented with three bits, but in this case the counter must be restricted to six states. To make sure this happens, D11, D12 and R6 are used to reset the counter to its initial state when it reaches the seventh state, which means when it reaches a binary count of 110. When this happens, pins 4 and 5 of the IC are both logic ‘1’ (high level), which causes a logic ‘1’ to be applied to pin 12 via resistor R6. This causes the counter to be reset, which is what we want.

The display consists of seven LEDs arranged in the same pattern as the usual markings on a normal die. This arrangement is shown in the schematic diagram. Before you begin thinking about the proper logical connections between the LEDs and the counter outputs, you can start by noting that except for the ‘1’ state there will always be two LEDs lit up at the same time. This means that only four distinct indications are necessary, instead of seven (with a total of seven LEDs).

Another advantage of this is that the current consumption can be reduced by connecting pairs of LEDs in series. Resistors R1–R4 limit the current through the LEDs to approximately 2 mA. This means you have to use low-current LEDs. They are nice and bright at a current of 2 mA. Resistor R3 has a higher value because only one LED is driven via it. For convenience, the circuit is dimensioned based on using a 9-V battery. The current consumption of the circuit depends on the number of LEDs that are illuminated, and with our prototype it varied over a range of approximately 2.5 mA to 6.5 mA.

The LEDs still produce enough light even when the supply voltage is as low as 6 V, but this depends strongly on the characteristics of the low-current LEDs used in the circuit. Diodes D8–D10 and transistor T1 are necessary to enable all the states of a normal die to be shown. By that, we primarily mean the states with two or three spots, which must be located diagonally. For readers who want to delve more deeply into the design, the following table shows the six different binary states, which LEDs are lit up for each state, and the number of spots shown by the die.

The die is operated by switch S1. In the quiescent state, the break contact of S1 is closed and the oscillator is stopped because the input of the oscillator stage is connected to ground via the switch. When S1 is pressed, the oscillator starts running and causes the states of the LEDs to change at a rate of 1 kHz, which is too fast to follow with the naked eye. This high frequency ensures that the state of the die is purely random when S1 is released, so there is no regularity or pattern in the results.

The circuit can be assembled on a small piece of perforated prototyping board. Fit the LEDs in exactly the same pattern as shown in the schematic diagram, since otherwise the spot patterns will not correspond to a real die. When you have assembled the circuit board, fit it in a plastic enclosure along with a 9-V battery to provide power.
Source: Elektor Electronics 12-2006

Read more

Pulse Rate Monitor

This simple circuit enables you to listen to your heartbeat, for instance, while you are exercising. The transducer used for detecting the pulse is an electret microphone, X1 in the diagram. The model used has two (polarized) terminals. As usual with this type of microphone, it functions via a series resistor, R1. The potential drop across this resistor is applied to op amp IC1a via C1. The amplification of the op amp is set to between ´40 and ´1000 with preset P1. Network R4-C3 in the feedback loop of IC1a is a low-pass filter with a cut-off frequency of 34 Hz. Higher frequencies are not needed for the present application. A pulse rate of 180* is equivalent to a frequency of 3 Hz.

So as to cater for a wide range of pulse rates, the cut-off frequency is made just over 11 times as high as that representing the highest pulse rate. Operational amplifier IC1c, in conjunction with push-pull am-plifier T1-T2, creates a headphone amplifier, whose output resistance is equivalent to the value of R9, that is, 47 Ω. This makes the circuit usable for virtually any kind of headset. The output is short-circuit-proof. In case of certain headphones, such as that used with Sony Walkman™ sets, it is best to connect the two earphones in series. Operational amplifier IC1b is used as an active potential divider. The voltage across the actual divider, R5-R6, is half the supply voltage.

Pulse Rate Monitor Circuit Diagram

This voltage is buffered by IC1b, taken from the low-resistance output, pin 7, of this op amp and used as reference for IC1a, and as operating voltage for the electret microphone. The voltage is decoupled by C4 to remove any interference signals from it. The supply voltage for the pulse rate monitor is decoupled by capacitor C7, immediately after polarity protection diode D1. Owing to the use of CMOS op amps, the current drain does not exceed 10 mA, so that operation from a 9 V battery is perfectly feasible. A dry alkaline manganese battery will have a life of about 50 hours.

Unless you are a young superfit top-class athlete, you should see your GP immediately when you find you have a pulse rate of 180. As a general guide, the absolute maximum pulse rate for a young, very fit person is 180, for a middle-aged person, 160, and for an elderly person, 140. When exercising, the pulse rate of a not very fit person should not exceed 60% of these maxima.

Read more